Did you ever think about why for instant message apps like Messenger, SnapChat, WhatsApp, or WeChat can accommodate billions of people and still keeping its smooth experience? The functions of a chat app looks so simple, but it actually takes so much effort and so many people to develop it behind the scene! so, why is that?

In this short course, I will give you a global view about what the technical design of a large-scale chat app, it's challenges, and basic requirements to make a successful app. I will give a rough idea about how they do it, and what aspects that you should be careful for designing such an app. We will cover these aspects from client devices, front-end design, back end design security and performance. Each aspect involves some techniques to implement.

In addition, these technical concepts are not only just fit for designing a chat app, but also for any kind of apps that relaying on real-time connection. For example, some IoT system needs to exchange data between devices and back end in real time, or in live broadcast system, hosts communicate with the audiences in real time.

The course content is not only coming from my experience but also some experts' best practices. After you learned these concepts, you will have a better understanding about designing a better chat app or other instant message app.